U.S. patent number 8,995,355 [Application Number 12/629,323] was granted by the patent office on 2015-03-31 for wireless communication apparatus, method and a computer program enabling switching of communication channel based on interference detection.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is Hidetada Nago. Invention is credited to Hidetada Nago.
United States Patent |
8,995,355 |
Nago |
March 31, 2015 |
Wireless communication apparatus, method and a computer program
enabling switching of communication channel based on interference
detection
Abstract
A wireless communication apparatus that transmits data in
certain communication interval to a receiving apparatus, using one
or more communication channels among a plurality of adjacent
communication channels, is provided. The apparatus includes: a
setting unit configured to set the one or more communication
channels for transmitting the data; a transmission unit configured
to transmit the data using the one or more set communication
channels; and a detection unit configured to detect interference
with other wireless communication apparatuses, when the
transmission unit transmits the data using the one or more set
communication channels; wherein the setting unit changes the number
of the one or more communication channels based on a time duration
that the data transmission has been restrained due to the detected
interference, and the communication interval.
Inventors: |
Nago; Hidetada (Kawasaki,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nago; Hidetada |
Kawasaki |
N/A |
JP |
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Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
42284890 |
Appl.
No.: |
12/629,323 |
Filed: |
December 2, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100165964 A1 |
Jul 1, 2010 |
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Foreign Application Priority Data
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Dec 26, 2008 [JP] |
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2008-335222 |
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Current U.S.
Class: |
370/329; 370/333;
370/328; 370/330; 370/332; 370/331 |
Current CPC
Class: |
H04W
28/20 (20130101); H04W 72/082 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
Field of
Search: |
;370/338,337,339,328,329,330 ;455/517,219,225,551,560 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-198867 |
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Jul 2002 |
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JP |
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2003-348635 |
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Dec 2003 |
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JP |
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2004-260528 |
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Sep 2004 |
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JP |
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2005-333510 |
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Dec 2005 |
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JP |
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2006-217491 |
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Aug 2006 |
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JP |
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2007-005897 |
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Jan 2007 |
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JP |
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2007-081836 |
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Mar 2007 |
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JP |
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2007-096786 |
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Apr 2007 |
|
JP |
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2008-199102 |
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Aug 2008 |
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JP |
|
Other References
US. Appl. No. 12/652,723, filed Jan. 5, 2010, Inventor Hidetada
Nago. cited by applicant .
Japanese Office Action issued on Jan. 7, 2013, in counterpart
Japanese Patent Application No. 2008-335222. cited by
applicant.
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Primary Examiner: Renner; Brandon
Assistant Examiner: Musa; Abdelnabi
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. A wireless communication apparatus that performs communication
using one or more communication channels, comprising: a
transmission unit configured to periodically transmit data; a
computer-readable memory constructed to store computer-executable
process steps; and a processor constructed to execute the
computer-executable process steps stored in the memory, wherein the
process steps stored in the memory cause the processor to: detect
an occurrence of interference in a communication channel used by
the apparatus, the interference being due to another communication
apparatus; wherein the transmission unit is configured to restrain
transmission of data when the occurrence of interference is
detected; wherein the process steps stored in the memory further
cause the processor to calculate a remaining time to transmit the
restrained data, based on a time period during which the restrained
data is to be transmitted and a length of the restrained time, to
determine whether transmission of the restrained data will be
completed within the remaining time, based on the length of the
restrained time and an estimated time period required for the
transmission of the restrained data, wherein it is determined that
the transmission of the restrained data will not be completed
within the remaining time if the length of the remaining time is
less than the estimated time period, and to increase a total number
of communication channels used by the apparatus in a case that it
is determined that the transmission of the restrained data will not
be completed within the remaining time.
2. The apparatus according to claim 1, wherein the process steps
stored in the memory further cause the processor to measure the
length of the restrained time in response to the detection of the
occurrence of interference.
3. The apparatus according to claim 1, wherein the process steps
stored in the memory further cause the processor to estimate the
time period required for the transmission of the restrained
data.
4. The apparatus according to claim 1, wherein the number of
communication channels is increased when a predetermined number of
determinations is made that the transmission of the restrained data
will not be completed within the remaining time.
5. The apparatus according to claim 1, wherein the number of
communication channels is increased by allowing the apparatus to
additionally use a communication channel adjacent to a
communication channel currently being used by the apparatus.
6. The apparatus according to claim 1, that performs communication
conforming with IEEE 802.11 series.
7. A wireless communication method performed by a wireless
communication apparatus using one or more communication channels,
the method comprising: periodically transmitting data; detecting an
occurrence of interference in a communication channel used by the
apparatus, the interference being due to another communication
apparatus; restraining transmission of data when the occurrence of
interference is detected; calculating a remaining time to transmit
the restrained data, based on a time period during which the
restrained data is to be transmitted and a length of the restrained
time; determining, whether transmission of the restrained data will
be completed within the remaining time, based on the length of the
restrained time and an estimated time period required for the
transmission of the restrained data, wherein it is determined that
the transmission of the restrained data will not be completed
within the remaining time if the length of the remaining time is
less than the estimated time period; and increasing a total number
of communication channels used by the apparatus in a case that it
is determined that the transmission of the restrained data will not
be completed within the remaining time.
8. A non-transitory computer-readable storage medium storing a
computer program that causes a wireless communication apparatus
using one or more communication channels to perform a method
comprising: periodically transmitting data; detecting an occurrence
of interference in a communication channel used by the apparatus,
the interference being due to another communication apparatus;
restraining transmission of data when the occurrence of
interference is detected; calculating a remaining time to transmit
the restrained data, based on a time period during which the
restrained data is to be transmitted and a length of the restrained
time; determining whether transmission of the restrained data will
be completed within the remaining time, based on the length of the
restrained time and an estimated time period required for the
transmission of the restrained data, wherein it is determined that
the transmission of the restrained data will not be completed
within the remaining time if the length of the remaining time is
less than the estimated time period; and increasing a total number
of communication channels used by the apparatus in a case that it
is determined that the transmission of the restrained data will not
be completed within the remaining time.
9. The apparatus according to claim 1, wherein the total number of
communication channels used by the apparatus is increased in a case
that the increase of the total number of communication channels
causes the transmission of the certain data to complete by the
certain time.
10. The apparatus according to claim 1, wherein the communication
channels used by the apparatus in a case that it is determined that
the transmission of the restrained data will not be completed
within the remaining time includes the communication channel in
which the occurrence of interference has been detected.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wireless communication
apparatus, a wireless communication method and a computer
program.
2. Description of the Related Art
For realizing high speed wireless LAN communication, IEEE 802.11n
standard that utilizes MIMO technology has been proposed. In IEEE
802.11n standard, wireless communication apparatus can select 20
MHz or 40 MHz as the communication bandwidth. In IEEE 802.11a,
which is in the same 5 GHz band as the IEEE 802.11n, a single
communication channel is stipulated to 20 MHz bandwidth. However,
in practice, a wireless communication apparatus conformed to IEEE
802.11a standard conduct communication using a 26 MHz bandwidth.
Therefore, interference is occurred not only with the same
communication channel, but also among the adjacent communication
channels. This is explained using the FIG. 8.
FIG. 8 is a figure showing the channel interval, as well as a
figure for explaining the image of used frequency spectrum.
Frequency spectrum 801 shows the frequency spectrum used for
conducting communications using the channel N. Since the actual
bandwidth of the frequency spectrum 801 is 26 MHz, there are
frequency spectrum parts that overlap with the N+1 and N-1 channel
frequency spectrum. Therefore, when there are two wireless
communication apparatuses located within proximity, not only when
the communication channels are equal, but also when communication
channels are adjacent to each other, the interference is occurred.
As a result, in carrier-sense before the data transmission, this
may be seen as existence of a carrier and therefore the packet
communication from one of the wireless communication apparatuses
may be restrained.
Even when the packet transmission is restrained as mentioned above
due to the interference, there may be cases that it is not a
problem if the communication peer receives all the packets at the
end. However, when data transmission is conducted within limited
timeframe such as in video streaming, throughput is decrease due to
the transmission restrain occurred by the adjacent channel
communication; as a result, image quality decreasing effects such
as image disturbance and delay is occurred.
As examples, the examples given in FIG. 9 and FIG. 10 are
considered. FIG. 9 shows a figure for explaining the case of two
wireless communication apparatuses conducting communication using
two adjacent channels. FIG. 10 shows a figure for explaining the
case of two wireless communication apparatuses conducting
communication using the same communication channel. In FIG. 9, a
Web camera 901 and a PC 902 are considered to be conducting video
stream communication. The Web camera uses the channel N and the PC
902 uses the channel N+1. The Web camera 901 and the PC 902 is in
adjacent, the transmission restrain cannot be ignored, which could
lead to a significant through-put decrease. Moreover, as shown in
the example of FIG. 10, even in case the Web camera 1001 and the PC
1002 is conducting communication within the same network, due to
interference, decrease in the quality of the video stream is
occurred.
To prevent such a throughput decrease, in Japanese Patent Laid-Open
No. 2004-260528, when the interfering wave of the adjacent channel
is detected, a technology for narrowing the bandwidth of the band
pass filter which is used to pass the signal of the currently used
channel, has been proposed. In Japanese Patent Laid-Open No.
2005-333510, when interference due to the adjacent station is
detected, changing the channel to a channel that does not affected
by the adjacent station, has been proposed. In Japanese Patent
Laid-Open No. 2006-217491, when the carrier of the adjacent station
is detected, a technology for changing the antenna directivity so
that the antenna does not receive carrier of the adjacent station,
has been proposed. In particular, there are also cases such as
changing the communication channel in order to avoid interference
as in Japanese Patent Laid-Open No. 2005-333510. However, in case
of Wireless LAN, it is necessary to change the channel at the
access point side; therefore, changing from the terminal side is
not possible. Further, in case channel is changed while
communicating, the communication will be cutoff. Further, when the
antenna directivity has been changed, as in Japanese Patent
Laid-Open No. 2006-217491, interferences due to other stations can
be avoided, however avoiding interferences due to station itself
cannot be conducted. Furthermore, in apparent when the signals of
the other stations are not visible, the station itself will conduct
communication regardless whether the other stations are
communicating or not; therefore, collation occurs in the wireless
domain, resulting increase in the communication error
frequency.
The present invention proposes a technology that reduces the
through-put decrease, even in case there are interferences with the
other wireless communication apparatuses.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a wireless
communication apparatus that transmits data in certain
communication interval to a receiving apparatus, using one or more
communication channels among a plurality of adjacent communication
channels, comprises: a setting unit configured to set the one or
more communication channels for transmitting the data; a
transmission unit configured to transmit the data using the one or
more set communication channels; and a detection unit configured to
detect interference with other wireless communication apparatuses,
when the transmission unit transmits the data using the one or more
set communication channels; wherein the setting unit changes the
number of the one or more communication channels based on a time
duration that the data transmission has been restrained due to the
detected interference, and the communication interval.
Further features of the present invention will become apparent from
the following description of exemplary embodiments (with reference
to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate embodiments of the
invention, and together with the description, serve to explain the
principles of the invention.
FIG. 1 is a figure showing an exemplary functional block diagram of
the wireless communication apparatus 100 according to the present
invention;
FIG. 2 is a figure showing an exemplary hardware block diagram of
the wireless communication apparatus 100 according to the present
invention;
FIG. 3 is a figure for explaining an exemplary case where 40 MHz
communication bandwidth can be used for communicating packets
within each communication interval by the wireless communication
apparatus;
FIG. 4 is a figure for explaining an exemplary case where 20 MHz
communication bandwidth can be used for packet communication within
each communication interval by the wireless communication
apparatus;
FIG. 5 is a flow chart showing an exemplary functional flow of the
wireless communication apparatus 100 according to the present
invention;
FIG. 6 is a flow chart showing an exemplary communication channel
setting process according to the present invention;
FIG. 7 shows an exemplary case where packet transmission within the
communication duration is possible by changing the bandwidth to 40
MHz;
FIG. 8 shows the channel interval and an image of used frequency
spectrum for explanation;
FIG. 9 shows a figure for explaining the case of two wireless
communication apparatuses conducting communication using two
adjacent channels; and
FIG. 10 shows a figure for explaining the case of two wireless
communication apparatuses conducting communication using the same
communication channel.
DESCRIPTION OF THE EMBODIMENTS
Hereinafter, the embodiments according to the present invention
will be explained with reference to the attached figures. The
present invention is applicable to a wireless communication
apparatus that conducts communication by sending generally constant
size data in generally constant communication intervals, using one
communication channel and one of the two communication channels
adjacent to aforementioned communication channel.
In the following embodiment, among the wireless communication
apparatus of this kind, specifically a wireless communication
apparatus compliant with the IEEE 802.11n standard is used as an
example. As mentioned earlier, in IEEE 802.11n, among the 20 MHz
bandwidth communication channels, communication can be conducted by
using one channel or adjacent two channels. In case two
communication channels are used, communication can be conducted
with 40 MHz bandwidth. In the following embodiment, the wireless
communication apparatus is considered to be sending constant size
packets within each communication duration that has a constant time
communication interval. Here, the time point that starts the
communication interval is called communication-timing. In addition,
in the present invention the destination of a packet can be any
apparatus, therefore, it is indicated as a receiving apparatus, and
in the following discussion the destination of the packet is
abbreviated.
First Embodiment
The construction of the wireless communication apparatus 100
according to the present invention is described using the FIGS. 1
and 2. The FIG. 1 is a figure showing an exemplary functional block
diagram of the wireless communication apparatus 100 according to
the present invention. The wireless communication apparatus 100
comprises a setting unit 101, an estimation unit 102, a
transmission unit 103, a detection unit 104, a measuring unit 105
and a calculation unit 106.
The setting unit 101 sets the communication channel for data
communication. As discussed before, the setting unit 101 can choose
the bandwidth as 20 MHz or 40 MHz. Moreover, the setting unit 101
sets which channel(s) is used for communication, among the
plurality of channels. The estimation unit 102 estimates the time
required for packet transmission.
Hereinafter, the time required for a packet transmission is called
required-time. The required-time changes depending on whether the
wireless communication apparatus 100 is using 20 MHz or 40 MHz as
the bandwidth. When the wireless communication apparatus 100 is
using 40 MHz, compared to the time required when 20 MHz is being
used, the packets can be transmitted with half the time.
The transmission unit 103 communicates the packets using the
channel(s) configured by the setting unit 101. The detection unit
104, using such as carrier-sense, detects interference due to
carriers used by the other wireless communication apparatuses. In
case the detection unit 104 detects an interference with a carrier
signal of other wireless communication apparatus, the packets
transmitted by the transmission unit 103 is restrained. As
explained above, interference may occur not only when the other
wireless communication apparatus 100 is using the same channel, but
also when the other wireless communication apparatus is using
adjacent channels. In case the wireless communication apparatus 100
is using the 40 MHz bandwidth, in other words two channels are
being used, the detection unit 104 may conduct detection of
interference for each of the used channels one by one.
The measuring unit 105 evaluates the time period the transmission
is being restrained by the transmission unit 103 for each
communication durations, due to interferences of carries used by
other wireless communication apparatus. In case the wireless
communication apparatus 100 is using 40 MHz bandwidth, in other
words using two channels been used, the measuring unit 105 may
calculate the restrained time for each channel one by one. The
calculation unit 106 calculates the remaining time. The remaining
time is the value obtained by subtracting the communication
restrained time from the communication interval.
FIG. 2 is a figure showing an exemplary block diagram of the
hardware of wireless communication apparatus 100. Here, FIG. 2 is
only an example of the wireless communication apparatus 100
according to the present invention, all the parts that are
represented is not necessary for the wireless communication
apparatus 100.
The CPU 201, which is a microprocessor, controls the wireless
communication apparatus 100 based on a program stored in a ROM 203,
a hard disk (HD) 212 or a recording media set in an external memory
drive 211. The CPU 201, as an example, may function as a setting
unit 101, an estimation unit 102, and a calculation unit 106.
A RAM 202 functions as a work area of CPU 201, and saves the
program stored in such as a ROM 203 and the hard disk 212. In the
ROM 203, a recording media set into the external memory drive 211
or the hard disk 212, as represented in a flow chart which is
explained later, a computer program executed by the CPU 201 and
etc. are recorded.
205 is a keyboard controller (KBC) that controls the input from a
keyboard (KB) 209, and pointers such as mouse which are not
represented in figures. 206 is a display controller (DPC) that
controls a display 210. 207 is a disk controller (DKC) that
controls access to the hard disk 212 and the external memory drive
211; it reads out, each program, font data, user file, editing
files and the like from each recording media. 208 is a network
controller (NC) that conducts communication with the network 220.
The network controller 208, as an example, functions as the
transmission unit 103, the detection unit 104, and the measuring
unit 105.
In addition, the CPU 201, as an example, executes processing of
outline font expansion (rasterization) to assigned display
information area of the RAM 202, or dedicated video memory (VRAM),
and makes it possible to display on the display 210. Further, the
CPU 201, based on the command given using the mouse cursor on the
display 210, opens windows of recorded type for conducting various
type of data processing.
Next, by using the FIGS. 3 and 4, the effects of selecting the
suitable bandwidth by the wireless communication apparatus will be
described. FIG. 3 is a figure for explaining an exemplary case
where 40 MHz communication bandwidth can be used for communicating
packets within each communication interval by the wireless
communication apparatus. FIG. 4 is a figure for explaining an
exemplary case where 20 MHz communication bandwidth can be used for
communicating packets within each communication interval by the
wireless communication apparatus. In FIGS. 3 and 4 the wireless
communication apparatus A and wireless communication apparatus B
are considered to be communicating respectively. Further, the
packets form the wireless communication apparatus A is represented
as "P_A" and the packets form the wireless communication apparatus
B is represented as "P_B".
In upper figure of FIG. 3, the wireless communication apparatus A,
communicates packets that require communication time
(required-time) of 7 ms, in each 10 ms communication interval, by
using the channel N. Moreover, the wireless communication apparatus
B, communicates packets that require communication time
(required-time) of 6 ms, by using the channel N+1, with a
communication interval of 10 ms. Moreover, it is considered that
the communication-timing of the wireless communication apparatus A
comes after communication-timing of 4 ms of the wireless
communication apparatus B.
At the timing t=0, the wireless communication apparatus B starts
communicating a packet 301. Since, the required time is 6 ms, this
packet communication completes at the timing t=6. The wireless
communication apparatus A, at the timing t=4, attempts to start
communication of a packet 302, since wireless communication
apparatus B is communicating in the adjacent channel, the
communication is restrained due to interference. As a result, the
communication of the packet 302 starts with a 2 ms delay 303 from
the conventional communication-timing. Similarly, the other arrows
shown in the figure indicates the delay from communication-timing.
At the timing t=10, wireless communication apparatus B attempts to
start communication of a packet 304; since wireless communication
apparatus A is communicating the packet 302 the communication is
restrained. As a result, the wireless communication apparatus B
starts communicating from the timing t=13.
As above, the delay gets accumulated in both wireless communication
apparatus A and wireless communication apparatus B. As result, for
instance, when wireless communication apparatus A is conducting
communication of a packet 305, packet communication cannot be
completed within the communication interval. Further, when wireless
communication apparatus A is conducting communication of a packet
306, packet communication cannot be started within the
communication interval. As above, throughput of both wireless
communication apparatuses gets reduced.
The lower figure of FIG. 3 is used for explaining a case similar to
the upper figure of FIG. 3; it only differs from the upper figure
from fact that the used bandwidth by the wireless communication
apparatus A is 40 MHz. By using 40 MHz bandwidth, transmitting
packets of the same size as the top figure of FIG. 3; it is
possible to transmit packets in 3.5 ms.
At timing t=0, wireless communication apparatus B starts
communication of a packet 351. Since the required-time is 6 ms,
this packet transmissions completes in the timing t=6. Wireless
communication apparatus A, at the timing t=4, attempts to start the
communication of a packet 352, since the wireless communication
apparatus B is still conducting communication in the adjacent
channel, communication is restrained due to interference. As a
result, with a delay 353 of 2 ms from the conventional
communication-timing, communication of the packet 352 is started.
Since communication of the packet 352 is completed in 3.5 ms, at
timing t=9.5 communication of the packet 352 is completed.
Therefore, wireless communication apparatus B can start
communicating a next packet 354 from the timing t=10.
As above, by using the 40 MHz bandwidth, although a delay occurs,
the wireless communication apparatus A, completing the packet
communication within the communication duration. Further, wireless
communication apparatus B is also able to complete packet
communication within the communication duration.
As an example, when 20 MHz bandwidth is used, in comparison to the
case when there is no interference from other wireless
communication apparatus, the throughput is reduced by 50%; however,
if 40 MHz bandwidth is used, the throughput reduction can be limit
to 33%. The betterment effects are not limited to the wireless
communication apparatus that changed the bandwidth, but also the
effects applied similarly to the other wireless communication
apparatus that happened to be the source of interference.
In upper figure of FIG. 4, the wireless communication apparatus A,
communicates packets with required-time of 3 ms, in each 7 ms
communication interval, by using the channel N and channel N+1.
Moreover, the wireless communication apparatus B, communicates
packets with required-time of 6 ms, in each 10 ms communication
interval, by using the channel N+2. Furthermore, the timing of
wireless communication apparatus A is coming after 1 ms of the
communication-timing of the wireless communication apparatus B.
In timing t=0, the wireless communication apparatus B starts
communication of a packet 401.
Since, the required time is 6 ms, this packet communication
completes at the timing t=6. The wireless communication apparatus
A, at the timing t=1, attempts to start communication of a packet
402, since wireless communication apparatus B is already
communicating in the adjacent channel, the communication is
restrained due to interference. As a result, the communication of
packet 402 starts with a 5 ms delay 403 from the conventional
communication-timing. Subsequently, after wireless communication
apparatus A complete communication of the packet 402, at timing
t=9, immediately starts communicating a next packet 404. At the
timing t=10, wireless communication apparatus B attempts to start
communication of a packet 405, since the wireless communication
apparatus A is communicating a packet 404, the communication is
restrained. As a result, the wireless communication apparatus B
starts communication form the timing t=12.
Also in upper figure of FIG. 4, as an example, in case the wireless
communication apparatus A communicating the packet 402 and a packet
406, completing the communication within the communication interval
is not possible. Further, when the wireless communication apparatus
A communicates a packet 407, starting the communication within the
communication interval is impossible.
The lower figure of FIG. 4 is used for explaining a case similar to
the top figure of FIG. 4; it only differs from the upper figure
from fact that the used channel is channel N with bandwidth of 20
MHz. Because wireless communication apparatus A uses 20 MHz
bandwidth, packets with similar size to the ones in upper figure
can be communicated with 6 ms. In this case, interference between
channel N and channel N+2 is not occurred; therefore, the wireless
communication apparatus A and the wireless communication apparatus
B both can conduct packet communication within
communication-timing.
As described above in FIGS. 3 and 4, by using a proper bandwidth,
high QoS communication can be realized, and the throughput of the
total wireless system increases. In the wireless communication
apparatus 100 according to the present invention, communication is
conducted by selecting the proper bandwidth of 40 MHz or 20 MHz,
for each communication duration. As an example, it is possible to
apply the wireless communication apparatus 100 according to the
present invention, to the wireless communication apparatus A of
FIGS. 3 and 4.
Here, it is to be understood that the wireless communication
apparatus B does not have to be a wireless communication apparatus
100 according to the present invention, since it is always
communicating in 20 MHz bandwidth. For an example, as a standard
that communicate within the same bandwidth as IEEE 802.11n IEEE
802.11a can be given; therefore, the wireless communication
apparatus B can be an apparatus that is only compliant with IEEE
802.11a standard. Even in this case, by applying the present
invention to the wireless communication apparatus A, the throughput
of the wireless communication apparatus B is increased. The
wireless communication apparatus 100 according to the present
invention selects the bandwidth used for packet transmission.
Therefore, the wireless communication apparatus 100 can function as
an access point or a station communicating with an access
point.
Subsequently, the functionality of wireless communication apparatus
100 will be discussed using the FIGS. 5 and 6. The FIG. 5 is a
flowchart showing the operation of the wireless communication
apparatus 100. The operations represented in the flow chart are
implemented by executing the computer program read into the RAM 202
by the CPU 201.
In step S501, the transmission unit 103 obtains the transmission
information. The transmission information is the information
necessary for transmitting data by the wireless communication
apparatus 100; as examples, it includes the address of the
destination apparatus, data to be transmitted, communication
interval of packet, and packet size. The way this information is
obtained is not limited to a specific manner. As an example, it is
possible for the wireless communication apparatus 100 to receive
information specified by the user for each data to be transmitted,
or calculate the necessary information based on predefined rules,
by the transmission unit 103. Further, based on the data size to be
communicated, communication interval of the packets and size of the
packets can be calculated.
In step S502, the setting unit 101 sets the communication channel
and the bandwidth to be used. As the communication channel, a
random channel among the channels that is not used, or a user (or
another apparatus) assigned channel, may be used. As the bandwidth,
either 20 MHz or 40 MHz may be used.
In step S503, the estimation unit 102 estimates the required-time,
which is the time interval from the start of sending a packet to
the end of the sending of the packet, based on the bandwidth and
the packet size. As an example, in step S502, in case 20 MHz is
been set as the bandwidth, the estimation unit 102 estimates the
required-time when the communication is conducted in 20 MHz. The
estimation unit 102 may also estimate the require-time for
bandwidth which is not been set at the same time. As an example, in
step S502, in case the 20 MHz is set as the bandwidth, the
estimation unit 102 may also estimate the required-time for the
case communication is conducted in 40 MHz.
In step S504, the transmission unit 103 determines whether it is
communication-timing or not. In case it the communication-timing
("YES" in step S504), the process proceeds to the step S505. In
case it is not the communication-timing ("NO" in step S504) the
process repeats the step S504.
In step S505, the detection unit 104, by such as carrier sensing,
determines whether any interference with carriers used by other
wireless communication apparatus is occurred or not. In case
interface is not occurred ("NO" in step S505), the process proceeds
to the step S510, the transmission unit 103 starts packet
transmission. In this case, packet transmission can be conducted in
the scheduled communication-timing. On the other hand, if
interference is occurred (YES in step S505) the process proceeds to
the step S506. As examples, in cases such as upper figure of FIG. 3
and upper figure of FIG. 4 interference occur.
In step S506, the measuring unit 105 starts restrained-time
calculations. The restrained-time of a wireless communication
apparatus is the time that packet communication of itself is
restrained due to interference with other wireless communication
apparatus. Here, incase bandwidth is set to 40 MHz, the measuring
unit 105 may measure the restrained-time for each communication
channel. As an example, the upper figure of FIG. 4, the packet 402
transmission of wireless communication apparatus A is been
restrained by the packet 401 transmitted using the communication
channel N+2. In this case, the channel that interferes with the
channel N+2 is channel N+1 and channel N is not interfered with the
channel N+2. Here, the detection unit 104, detects interference for
each communication channel, and the measuring unit 105 measures
restrained-time for each communication channel.
In step S507, the detection unit 104 determines whether
interference is dissolved or not. In case the interference is
dissolved ("YES" in step S507), the measuring unit 105 stops
calculating restrained time, record the restrained-time, as an
example, in RAM 202 etc. Then, the process proceeds to step S508.
Similarly, even in this case restrained-time can be recorded for
each communication channel. In case the interference is not been
dissolved ("NO" in step S507), the process repeats the step
S507.
In step S508, the calculation unit 106 calculates the remaining
time of the present communication duration. The remaining time is
the value obtained by subtracting the restrained-time, which is
recorded in the step S507, from the communication interval. If
packet communication could be completed within the remaining time,
it means the wireless communication apparatus 100 can complete the
packet communication within the communication duration.
In step S509, the wireless communication apparatus 100 conducts the
communication channel setting process. Here, based on the remaining
time calculated in the step S508, and the required time estimated
in the step S503, communication channel setting is conducted, the
details will be explained later. In step S510, the transmission
unit 103 transmits using the communication channel that is set in
step S509.
In step S511, the transmission unit 103 determines whether
transmitting the data is finished or not; in case it is not
finished ("NO" in step S511), the process returns to step S504 and
wait for the next communication-timing. In case it is finished
("YES" in step S511), the process is concluded.
Subsequently, using the FIG. 6, the communication channel setting
process in step S509 is explained in detail. FIG. 6 is a flow chart
showing an exemplary communication channel setting process. The
operation shown in the flowchart can be implemented by a computer
program read from the RAM 202 and executed at the CPU 201.
In step S601, the setting unit 101 compares the required-time of
the present bandwidth setting estimated in step S503, and remaining
time calculated in step S508. In case of the required time is less
than the remaining-time ("NO" in step S601), even in case the
packet is transmitted in the present communication channel setting,
the packet can complete communication within the
communication-duration. Therefore, without changing the
communication channel the process is concluded.
In case of the required time is larger than the remaining time
("YES" in step S601), the process proceeds to the step S602. In the
step S602, the setting unit 101 determines whether the present
bandwidth setting is equal to 40 MHz or not. In case the bandwidth
is not set to 40 MHz ("NO" in step S602), in other words, in case
the setting is 20 MHz, the process proceeds to the step S604. In
this case, by changing the bandwidth 40 MHz, it may be possible to
shortening the required-time and conducting packet transmission
within the communication-duration. Here, in step S604, the setting
unit 101, as the communication channel, a channel with bandwidth of
40 MHz including the preset communication channel is set.
An example of this case is explained using the FIG. 7. In FIG. 7
shows an exemplary case where packet transmission within the
communication duration is possible by changing the bandwidth to 40
MHz. Here, the status is the same as in FIG. 3, therefore,
explanation is abbreviated. The wireless communication apparatus
100 according to the present invention is considered to be
functioning as the wireless communication apparatus A in FIG. 3,
and conducting packet communication using the communication channel
N. That is, as the bandwidth 20 MHz is set.
Here, consider a case where timing t=14 is the
communication-timing. In this case, the detection unit 104 detects
that at channel N+1, the other wireless communication apparatus are
conducting communication of the packet 701. Therefore, the
transmission of packet 702 is restrained. When the transmission of
packet 701 is concluded, the calculation unit 106 calculates the
remaining time. As explained above in FIG. 3, the remaining time is
shorter than the required time of transmission. Here, the setting
unit 101 changes the bandwidth to 40 MHz, and then the transmission
unit 103 transmits the packet 702. Due to the bandwidth change as
explained above, the wireless communication apparatus 100 is able
to complete communication of the packet 702 within the
communication-duration.
By returning to the FIG. 6, in case the bandwidth setting is 40 MHz
("YES" in step S602), the process proceeds to the step S603. In
step S603, the setting unit 101 compares the required-time and
remaining time in case transmitted with a 20 MHz bandwidth. As
explained using the FIG. 4, in case the MHz is been used as the
bandwidth, compared to the case of 40 MHz bandwidth, although
required-time become longer, there may be cases that is possible to
prevent interference with other wireless communication apparatus.
Therefore, the calculation unit 106, based on the channel
communication restrained time calculated in step S506, calculates
the remaining time in case each communication channel transmits the
packet on its own.
The calculated remaining time for each communication channel is
compared with the required-time in case 20 MHz bandwidth is being
used as calculated in step S503. In case the ("NO" in step S603),
by changing the bandwidth to 20 MHz, the wireless communication
apparatus 100 can complete the packet communication within the
communication duration. Here, in step S604, the setting unit 101
changes the packet communication setting of the communication
channels by selecting one of the communication channels that
satisfies the requirement of step S603. On the other hand, even
when either of the channels are changed, in case the required time
is longer than the remaining time ("YES" in step S603), the setting
unit 101 concludes the process without updating the setting.
Meanwhile, in case only one communication channel is interfering
with a communication channel used by another wireless communication
apparatus, the communication channel may be changed into the
channel which is not interfered.
The communication channel setting process shown in FIG. 6 may start
by using the number of times communication is restrained within a
predefined time due to carrier sense, or continuous number of times
the communication is restrained due to carrier sense, as a
trigger.
The wireless communication apparatus 100 according to the
embodiment of the present invention, by changing the number of used
communication channels accordingly, is able to respite the
reduction of communication throughput of itself. Moreover, it is
possible to respite the reduction of communication throughput of
other communication channels that the communication channel itself
is interfering with. Furthermore, the communication does not break,
since this method only changes the used communication
bandwidth.
Other Embodiments
Aspects of the present invention can also be realized by a computer
of a system or apparatus (or devices such as a CPU or MPU) that
reads out and executes a program recorded on a memory device to
perform the functions of the above-described embodiment(s), and by
a method, the steps of which are performed by a computer of a
system or apparatus by, for example, reading out and executing a
program recorded on a memory device to perform the functions of the
above-described embodiment(s). For this purpose, the program is
provided to the computer for example via a network or from a
recording medium of various types serving as the memory device
(e.g., computer-readable medium).
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2008-335222 filed Dec. 26, 2008 which is hereby incorporated by
reference herein in its entirety.
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